Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE ALUMINUM ALLOYS America, Pittsburgh,

Pennsylvania N Drawing.

Pa., a corporation of Application September 21, 1932 Serial No. 634,170

1 Claim.

This invention relates to aluminum base alloys containing magnesium, nickel, and cobalt, and to certain alloys of this nature which have improved properties at elevated temperatures.

One of the important uses to which aluminum base alloys are put is as reciprocating parts operating at elevated temperatures, i. e., temperatures in the neighborhood of about 400 to 700 Fahrenheit. At these temperatures it is the common tendency of aluminum base alloys to decrease in strength, and the provision of alloys which will have a good strength at elevated temperatures and a substantial ductility is among the important problems of the art. Moreover,

such alloys, in order to be generally satisfactory must be light in weight and must have such casting characteristics as will allow the alloy to be readily cast to intricate shapes in permanent molds as well as sand molds.

We have discovered an alloy which has many of the foregoing characteristics. This one is one which contains 3.0 to 8.0 per cent by weight of magnesium, 0.5 to 4.0 per cent by weight of nickel, 0.05 to 0.4 per cent of at least one of a 2 class of elements defined to be antimony and bismuth, and 0.1 to 3.0 per cent by weight of cobalt, the balance being principally aluminum. This alloy has, at elevated temperatures, a strength which is greater than many of the alloys heretofore known and combines with such strength an adequate ductility, good casting characteristics, and a lightness of weight conducive to its use in the manufacture of reciprocating parts.

As exemplary of the excellent properties of the alloy at elevated temperatures is the case of an alloy containing 6 per cent magnesium, 2 per cent nickel, 1.5 per cent cobalt, and 0.1 per cent antimony, the balance being principally aluminum. This alloy in the form of a sand casting was heated for 4 hours at 700 Fahrenheit and cooled to 600 Fahrenheit. It was then maintained at 600 Fahrenheit for 10 days and tested at this temperature. The tests showed a tensile strength of 16,525 pounds per square inch and an elongation of 2.0 per cent in 2 inches. An indication of the improved properties of our new alloys may be obtained by comparing these properties with those of an alloy of exactly the 5 same composition with the exception that no antimony was present, which alloy was in the sand cast form. This alloy was similarly treated and tested. The tests showed the casting to have 0 a tensile strength of 16,260 pounds per square inch, and an elongation of 0.5 per cent in 2 inches.

.The alloying elements antimony and bismuth have, in the small amounts indicated, substantially similar properties, their main function be- 0 ing, as we have discovered, to prevent a too substantial decrease of ductility at elevated temperatures. These elements may be present separately or they may be added together, but, either together or separately, they should not, we have found, exceed about 0.4 per cent since in much greater amount they tend to decrease the ductility of the alloy.

The alloys of the present invention may be manufactured by any of the usual methods such 70 as melting the aluminum and adding thereto the other metals.

Another property of these alloys is their improved fiuidity as compared with the alloys which have, heretofore, been widely used as a 75 material for parts operating at elevated temperatures. Comparative tests, based upon the distance that the molten alloy, originally heated to a given temperature, will fiow through a spiral formed in a sand mold, have shown that our 30 novel alloys are very superior with respect to fluidity.

The aluminum used in the manufacture of the alloys may be of the highest purity or it may contain amounts of usual impurities, and 5 the term aluminum as used herein and in the claim designates the aluminum of com-. merce. It is an incidental property of our alloys that the presence of iron in amounts as high as 2 per cent by weight is not harmful 0 to the high temperature properties of the alloys and, therefore, a wide choice between the various grades of commercial aluminum is possible.

We claim:

A metallic alloy characterized by high phys- 5 ical and tensile properties at elevated temperatures and good fluidity and consisting of 3.0 to 8.0 per cent by weight of magnesium, 0.5 to 4.0 by weight of nickel, 0.1 to 3.0 per cent by weight of cobalt, and 0.05 to 0.4 per cent by weight of at least one of the class of metals antimony and bismuth, the total amount of the antimony and/0r bismuth being not greater than 0.4 per cent by Weight, the balance being aluminum.

WALTER A. DEAN. LOUIS W. KEMPF. 

